From 09b7ed600bfda6f708db85cd850c0539c3448a0a Mon Sep 17 00:00:00 2001
From: Tim Burke <tim.burke@gmail.com>
Date: Wed, 5 Feb 2020 08:36:24 -0800
Subject: [PATCH] sharding: filter shards based on prefix param when listing

Otherwise, we make a bunch of backend requests where we have no
real expectation of finding data.

Change-Id: I7eaa012ba938eaa7fc22837c32007d1b7ae99709
---
 swift/proxy/controllers/container.py          | 13 ++++++++++
 test/unit/proxy/controllers/test_container.py | 25 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/swift/proxy/controllers/container.py b/swift/proxy/controllers/container.py
index 6ab0ada3a7..2235db757c 100644
--- a/swift/proxy/controllers/container.py
+++ b/swift/proxy/controllers/container.py
@@ -166,6 +166,7 @@ class ContainerController(Controller):
         reverse = config_true_value(params.get('reverse'))
         marker = wsgi_to_str(params.get('marker'))
         end_marker = wsgi_to_str(params.get('end_marker'))
+        prefix = wsgi_to_str(params.get('prefix'))
 
         limit = req_limit
         for shard_range in shard_ranges:
@@ -200,6 +201,18 @@ class ContainerController(Controller):
                 headers = {'X-Backend-Record-Type': 'object'}
             else:
                 headers = None
+
+            if prefix:
+                if prefix > shard_range:
+                    continue
+                try:
+                    just_past = prefix[:-1] + chr(ord(prefix[-1]) + 1)
+                except ValueError:
+                    pass
+                else:
+                    if just_past < shard_range:
+                        continue
+
             self.app.logger.debug('Getting from %s %s with %s',
                                   shard_range, shard_range.name, headers)
             objs, shard_resp = self._get_container_listing(
diff --git a/test/unit/proxy/controllers/test_container.py b/test/unit/proxy/controllers/test_container.py
index b989fb6145..ba0e4fff1a 100644
--- a/test/unit/proxy/controllers/test_container.py
+++ b/test/unit/proxy/controllers/test_container.py
@@ -810,6 +810,31 @@ class TestContainerController(TestRingBase):
             query_string='?end_marker=%s' % end_marker)
         self.check_response(resp, root_resp_hdrs)
 
+        # GET with prefix
+        prefix = 'hat'
+        # they're all 1-character names; the important thing
+        # is which shards we query
+        expected_objects = []
+        mock_responses = [
+            (404, '', {}),
+            (200, sr_dicts, root_shard_resp_hdrs),
+            (200, [], shard_resp_hdrs[1]),
+        ]
+        expected_requests = [
+            ('a/c', {'X-Backend-Record-Type': 'auto'},
+             dict(prefix=prefix, states='listing')),  # 404
+            ('a/c', {'X-Backend-Record-Type': 'auto'},
+             dict(prefix=prefix, states='listing')),  # 200
+            (wsgi_quote(str_to_wsgi(shard_ranges[1].name)),
+             {'X-Backend-Record-Type': 'auto'},  # 404
+             dict(prefix=prefix, marker='', end_marker='pie\x00',
+                  states='listing', limit=str(limit))),
+        ]
+        resp = self._check_GET_shard_listing(
+            mock_responses, expected_objects, expected_requests,
+            query_string='?prefix=%s' % prefix)
+        self.check_response(resp, root_resp_hdrs)
+
         # marker and end_marker and limit
         limit = 2
         expected_objects = all_objects[first_included:first_excluded]